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Syntheses and crystal structures of cadmium(II) coordination polymers with end-to-end dicyanamide bridges
Polyhedron 21 (2002) 893 /898 www.elsevier.com/locate/poly
Syntheses and crystal structures of cadmium(II) coordination polymers with end-to-end dicyanamide bridges Jun-Hua Luo, Mao-Chun Hong *, Rong Cao, Yu-Cang Liang, Ying-Jun Zhao, Rui-Hu Wang, Jia-Bao Weng State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, People’s Republic of China Received 15 August 2001; accepted 25 January 2002
Abstract Two new derivatives of cadmium(II) dicyanamide (dicyanamide/[N(CN)2] , dca), [Cd(N(CN)2)2(phen)]n (1) and [Cd(N(CN)2)2(2,2?-bipy)]n (2), have been synthesized and structurally characterized. The cadmium(II) centers in 1 are connected through single or double end-to-end dca bridging ligand to form a 2-D layer structure, which furthermore condense into a 3-D structure through the p /p interaction between aromatic rings of adjacent layers. In 2, the cadmium(II) coordination sphere is a distorted octahedron, bound to four dca ligands and one chelate 2,2?-bipy ligand, and the adjacent cadmium(II) centers are bridged by the double end-to-end m1,5-N /C /N /C/N to form an extended structure with a zigzag 1-D chain, and a 2-D layer structure results from the p /p interactions of the adjacent chains. Crown Copyright # 2002 Published by Elsevier Science Ltd. All rights reserved. Keywords: Cadmium complexes; Dca ligand; Double end-to-end; Zigzag chain; p /p interaction
1. Introduction Metal-organic frameworks are widely regarded as promising materials for application in catalysis, separation and molecular recognition [1]. There have been numerous reports in which N-donor bridging ligands are used to form infinite metal-organic polymeric frameworks [2]. Dicyanamide, [N(CN)2], was selected due to its coordination versatility ranging from being monodentate to m4- coordination, and thus provides a suitable ‘building block’ for assembling novel inorganic/organic hybrid materials. Monodentate (terminal) coordination occurs in [Cu(II)(o -phen)2{N(CN)2}][C(CN)3] [3,3a], [Cu(II)(o -phen)2{N(CN)2}2] (o-phen /o-phenanthroline) [3b] and [Zn3(OAc)4(4,4?-bipy)3{N(CN)2}2] [3c]. Bidentate coordination has often been observed and
* Corresponding author. Tel.: 86-591-379-2460; fax: 86-591371-4946. E-mail address: [email protected] (M.-C. Hong).
was reported for Me2Sn[N(CN)2]2 [3d], Me3Sn[N(CN)2] [3d], two polymorphs of Ag[N(CN)2] [3e,3f], and Mn[N(CN)2]2(pyz) (pyz /pyrazine) [3g,3h]. Tri-coordinate m3-[N(CN)2] is observed in the rutile-type class of molecule-based magnets, M(II)[N(CN)2]2 (M /Co or Ni) [3i]. Unusual m4 coordination [1e] is also known and was found in the structures of Me2Tl[N(CN)2] [3j]. Structures reported recently include M(dca)2L2 chains, (4,4) sheets, diamond-like works, interpenetrating networks, molecular tubes and self-penetrating works [4]. In these materials, s-bond formation occurs through lone pair donation of the nitrile N atoms to an octahedral metal center. Our goal was to prepare and characterize new low-dimensional solids consisting of divalent transition metal complexes with the dicyanamide ligand. Herein, we report the syntheses, crystal structures, and vibrational properties of [Cd(N(CN)2)2(phen)]n (1) and [Cd(N(CN)2)2(2,2?-bipy)]n (2), the first structurally characterized cadmium(II) dicyanamide complexes.
0277-5387/02/$ - see front matter Crown Copyright # 2002 Published by Elsevier Science Ltd. All rights reserved. PII: S 0 2 7 7 - 5 3 8 7 ( 0 2 ) 0 0 8 6 8 - 9
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J.-H. Luo et al. / Polyhedron 21 (2002) 893 /898
2. Experimental
Table 1 Crystallographic data for the title two complexes
2.1. Materials and physical measures Elemental analyses were determined on an Elementar Vario ELIII analyzer. IR spectra were measured as KBr pellets on a Nicolet Magna 750 FT IR spectrometer in the range of 200/4000 cm 1. All reagents were commercially available and used as received. 2.2. Synthesis of the complexes 2.2.1. [Cd(N(CN)2)2(phen)]n (1) To an aqueous solution (20 ml) of Cd(NO3)2 ×/4H2O (0.155 g, 0.5 mmol), sodium dicyanamide (0.09 g, 1 mmol) was added. After stirring the mixture for about 30 min, the dmf solution (10 ml) of phen was added into it. The above mixture was stirred and heated for 1 h, then filtered when it was still hot. Well shaped crystals of [Cd(N(CN)2)2(phen)]n were obtained from the mother liquor by slow evaporation at room temperature (r.t.) for several days. They were filtered off, washed with a small mount of water, and dried in air. Yield 78%. Calc. for C16H8CdN8: C, 45.21; H, 1.88; N, 26.37. Found: C, 44.89; H, 2.01; N, 27.68%. 2.2.2. [Cd(N(CN)2)2(2,2?-bipy)]n (2) The compound was synthesized as 1 except 2,2?-bipy instead of phen. Yield 78%. Calc. for C14H8CdN8: C, 41.93; H, 2.00; N, 27.95. Found: C, 41.67; H, 1.85; N, 29.21%. 2.3. X-ray crystallography Single crystals with approximate dimensions 0.52 / 0.48 /0.40 mm for 1 and 0.42 /0.30 /0.25 mm for 2 were selected and coated with epoxy glue. Data collections was carried out on a Siemens Smart CCD diffractometer equipped with graphite-monochromated ˚ ) at 298 K. Intensities Mo Ka radiation (l/0.71073 A of both 1 and 2 were corrected for empirical absorption based on SADABS scan technique [5]. Their structures were solved by direct methods and all calculations were performed using the SHELXL-PC program [6]. The positions of H atoms were generated geometrically ˚ ), assigned isotropic thermal (C /H bond fixed at 0.96 A parameters. The structure was refined by full-matrix least-squares minimization of S(Fo/Fc)2 with anisotropic thermal parameters for all atoms except the H atoms. Table 1 gives a structure determination summary and Table 2 and Table 3 list the selected bond lengths and angles.
Empirical formula Formula weight Temperature (K) ˚) Wavelength (A Crystal system Space group Unit cell dimensions ˚) a (A ˚) b (A ˚) c (A a (8) b (8) g (8) ˚ 3) V (A Z Dcalc (Mg m 3) Absorption coefficient (mm 1) F (000) Crystal size (mm) u Range for data collection (8) Index ranges
Reflections collected Refinement method Data [I 2s (I )]/parameters Goodness-of-fit on F 2 R1 indices (I 2s (I )) Wr2 indices (all data) Largest difference peak ˚ 3) and hole (e A
1
2
C16H8CdN8 424.70 293(2) 0.71073 monoclinic P 2(1)/c 3D 10.1502(3) 10.9815(4) 14.5839(4) 90 99.609(1) 90 1602.78(9) 4 1.760 1.379
C14H8CdN8 400.34 293(2) 0.71073 monoclinic C 2/c 2D 6.6849(10) 17.476(2) 13.231(2) 90 91.142(3) 90 1545.4(4) 4 1.722 1.424
832 0.30 0.25 0.15 2.03 /25.06
784 0.27 0.21 0.15 2.33 /25.03
125 h 5 6, 135 k 5 12, 16 5 1 5 17 5804 Full-matrix leastsquares on F 2 2832/226
65 h 5 7, 20 5 k 5 10, 12 5 1 5 15 3086 Full-matrix leastsquares on F 2 1354/105
1.074 0.0328 0.779 0.513 and 0.471
1.005 0.0739 0.1818 0.44 and 0.734
Table 2 ˚ ) and angles (8) for [Cd(N(CN)2)2(phen)]n (1) Selected bond lengths (A Bond lengths Cd N(4) Cd N(3A) Cd N(7) C(1) N(1) C(2) N(3) C(3) N(4) C(4) N(6)
2.246(4) 2.291(4) 2.342(3) 1.143(5) 1.134(5) 1.123(5) 1.136(5)
Cd N(1) Cd N(8) Cd N(6B) C(1) N(2) C(2) N(2) C(3) N(5) C(4) N(5)
2.279(4) 2.322(3) 2.481(4) 1.291(5) 1.298(5) 1.291(6) 1.284(6)
Bond angles N(4) Cd N(1) N(1) Cd N(3A) N(1) Cd N(8) N(4) Cd N(7) N(3A) Cd N(7) N(4) Cd N(6B) N(3A) Cd N(6B) N(7) Cd N(6B)
94.30(16) 96.48(14) 98.04(13) 94.58(14) 98.51(12) 89.17(16) 177.70(13) 81.62(12)
N(4) Cd N(3A) N(4) Cd N(8) N(3A) Cd N(8) N(1) Cd N(7) N(8) Cd N(7) N(1) Cd N(6B) N(8) Cd N(6B)
93.10(15) 165.83(15) 92.40(12) 162.10(12) 71.68(11) 83.01(13) 85.46(13)
Symmetry transformations used to generate equivalent atoms: (A) x , y1/2, z1/2; (B) x1, y , z2; (C) x , y1/2, z1/2 for complex 1.
J.-H. Luo et al. / Polyhedron 21 (2002) 893 /898
895
Table 3 ˚ ) and angles (8) for [Cd(N(CN)2)2(2,2?-bipy)]n Selected bond lengths (A (2)
3. Results and discussion
Bond lengths Cd N(2A) Cd N(1) Cd N(4B) N(2) C(6) N(3) C(7)
2.304(12) 2.322(9) 2.346(13) 1.108(14) 1.252(16)
Cd N(2) Cd N(1A) Cd N(4C) C(6) N(3) C(7) N(4)
2.304(12) 2.322(9) 2.346(13) 1.237(16) 1.099(16)
3.1. IR spectroscopic study
Bond angles N(2A) Cd N(2) N(2) Cd N(1) N(2) Cd N(1A) N(2A) Cd N(4B) N(1) Cd N(4B) N(2A) Cd N(4C) N(1) Cd N(4C) N(4B) Cd N(4C)
103.7(5) 93.2(4) 162.6(4) 89.8(4) 95.5(4) 86.7(4) 89.2(4) 174.3(6)
N(2A) Cd N(1) N(2A) Cd N(1A) N(1) Cd N(1A) N(2) Cd N(4B) N(1A) Cd N(4B) N(2) Cd N(4C) N(1A) Cd N(4C)
162.6(4) 93.2(4) 70.4(5) 86.7(4) 89.2(4) 89.8(4) 95.5(4)
Symmetry transformations used to generate equivalent atoms: (A) x , y , z1/2; (B) x , y , z ; (C) x , y , z1/2.
At room temperature, the solid state infrared spectrum depicts several nCN bands at 2301m, 2260(sh), 2216s, 2177s, 2156s cm 1 in complex 1 and 2303m, 2206(sh), 2229s, 2156s cm 1 in complex 2, which are attributed to nsym/nasym(C /N), nasym(C /N) and nsym(C/N) modes, and are comparable to those of related compounds in Table 4. These bands differ significantly from those of Na[N(CN)2], which are at 2129, 2232 and 2286 cm1 [7]. The bands at 1365m, 916m in 1 and 1344m, 916m in 2 are assigned to nasym(C/N) and nsym(C /N), respectively.
Table 4 Comparison of nCN absorption of selected M(II)[N(CN)2]2Ln (n 1 or 2) complexes Complexes
n asym n sym (C N)
nasym(C N)
nasym(C N)
Reference
Mn[N(CN)2]2(py) Fe[N(CN)2]2(MeOH)2 Co[N(CN)2]2{iz}2 Ni[N(CN)2]2(tetramepz)2 Co[N(CN)2]2(2-meiz)2 Pd[N(CN)2]2{P(C6H5)3}2 Cu[N(CN)2]2(iz)2 [Cd(N(CN)2)2(phen)]n [Cd(N(CN)2)2(2,2?-bipy)]n
2295s 2306(sh), 2274m 2281s 2285vs 2279s 2310m 2292s 2301m,2260(sh) 2303m
2234m 2254s 2246s 2235(sh) 2250s 2240s 2250m 2216s 2229s
2167s 2178s,2154m 2185vs 2212vs,2165vs 2180vs,2150w 2180vs 2190s 2177s,2156s 2156s
[3g] [9] [10] [11] [10] [12] [13] this work this work
Fig. 1. An
ORTEP
drawing of [Cd(N(CN)2)2(phen)]n (1) with atomic numbering scheme.
J.-H. Luo et al. / Polyhedron 21 (2002) 893 /898
896
Fig. 2. The 2-D layer structure of [Cd(N(CN)2)2(phen)]n (1) (the terminal ligand Phen is omitted for clarity)
3.2. Crystal structure analysis 3.2.1. Crystal structure of complex 1 Fig. 1 shows an ORTEP [8] diagram of the coordination sphere of the Cd(II) ion and atom labeling in [Cd(N(CN)2)2(phen)]n (1). Each cadmium(II) atom lies on an inversion center, and is connected to three other cadmium(II) centers through four dca ligands, one double end-to-end dca bridge to one cadmium(II) atom and two single end-to-end dca bridges to another two cadmium(II) atoms. Thus, all cadmium atoms form
a 2-D layer structure through both the double end-toend dca bridges and single end-to-end dca bridges as in Fig. 2, and furthermore generate a 3-D structure through the weak p/p interaction between aromatic ˚ , as shown rings of adjacent layers with distances 3.584 A in Fig. 3. Each cadmium(II) center is six-coordinated and display a distorted octahedral coordination, with two terminal N atoms of two different dca ligands [Cd/ ˚ ] and two N atoms of N(1), 2.279(4); Cd /N(4), 2,246 A the phen ligand [Cd /N(7), 2.342 (3); Cd /N(8), 2.322(3) ˚ ] in the equatorial plane, while the other two N atoms A of two dca ligands [Cd /N(3A), 2.291(4); Cd /N(6B), ˚ ] occupy the axial positions. Two kinds of 2.481(4) A bond angles may be found in the equatorial plane: the lower of 71.688 corresponding to the N(phen)/Cd / N(phen) bond angle and three greater N(phen)/Cd / N(dca) bond angles [N(1) /Cd /N(8), 98.04(13)8; N(4) / Cd /N(7), 94.58(14)8] and N(dca)/Cd /N(dca) bond angles [N(4) /Cd /N(1), 94.30(16)8]. The four equatorial donor atoms and the central cadmium(II) atom determine a plane with maximum deviation for Cd of / 0.1628(5) A˚. Approximate C2v symmetry is observed for the dca ligand with C(2) /N(3), C(1) /N(1), C(4) / N(6) and C(3) /N(4) bond distances of 1.134(5), ˚ , respectively. The 1.143(5), 1.136(5) and 1.123(5) A lack of significant electron density near the amide nitrogen N2 and N5 results in longer C(1) /N(2), C(2) /N(2), C(3) /N(5) and C(4) /N(5) bond distances, ˚ , suggesting a small degree of p which average 1.291 A conjugation within the [N(CN)2] backbone [9].
Fig. 3. The 3-D structure of [Cd(N(CN)2)2(phen)]n (1) through the weak p /p interaction between adjacent layers
J.-H. Luo et al. / Polyhedron 21 (2002) 893 /898
Fig. 4. An ORTEP drawing of [Cd(N(CN)2)2(2,2?-bipy)]n (2) with atomic numbering scheme.
897
3.2.2. Crystal structure of complex 2 In complex 2, [Cd(N(CN)2)2](2,2?-bipy)], the adjacent cadmium(II) centers are bridged by the double end-toend m1,5-N /C /N/C /N to form an extended structure with a zigzag 1-D chain (Fig. 5). The cadmium(II) centers are bound to four dca ligands and one chelate 2,2?-bipy ligand (Fig. 4), the cadmium(II) coordination sphere is a distorted octahedron with two N atoms of ˚ ; Cd /N(2A), 2.304 A ˚ ] and two dca [Cd /N(2), 2.304 A two N atoms of the 2,2?-bipy ligand [Cd /N(1), 2.322(9) ˚ ; Cd /N(1A), 2.322(9) A ˚ ] in the equatorial plane, and A two N atoms of two other dca ligands [Cd /N(4B), ˚ ; Cd /N(4C), 2.346(13) A ˚ ] occupy the axial 2.346(13) A plane. The effect of the distortion is readily seen in cis N /Cd /N? bond angles, which vary from 70.4(5)8 to 103.(5)8 for N(1) /Cd /N(1A), N(1) /Cd /N(2) and N(2) /Cd /N(2A), respectively. [N(CN)2] bridging li-
Fig. 5. The chain structure of [Cd(N(CN)2)2(2,2?-bipy)]n (2).
Fig. 6. The 2-D structure of [Cd(N(CN)2)2(2,2?-bipy)]n (2) through the weak p /p interaction between adjacent chains.
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gands retain approximate C2v symmetry with C(7)/N(4) and C(6) /N(2) bond distances of 1.099(16) and ˚ , respectively. Weak p/p interactions are 1.108(14) A evident, with the shortest distance between the pyridine ˚ , thus forming a 2rings of adjacent chains being 3.641 A D sheets as in Fig. 6. [3]
4. Supplementary material Atomic coordinates, thermal parameters and bond lengths and angles for compounds 1 and 2 have been deposited at the Cambridge Crystallographic Center (CCDC). Any request to the CCDC for this material should quote the full literature citation and the reference numbers CCDC 162756 and 162757. Copies of this information may be obtained free of charge from The Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax: /44-1223-336033; e-mail: [email protected] or www:http://www.ccdc.cam.ac.uk).
Acknowledgements [4]
The authors are grateful to the National Nature Science Foundation of China and the Key Project of Chinese Academy of Science for financial support.
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Syntheses and crystal structures of cadmium(II) coordination polymers with end-to-end dicyanamide bridges Jun-Hua Luo, Mao-Chun Hong *, Rong Cao, Yu-Cang Liang, Ying-Jun Zhao, Rui-Hu Wang, Jia-Bao Weng State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, People’s Republic of China Received 15 August 2001; accepted 25 January 2002
Abstract Two new derivatives of cadmium(II) dicyanamide (dicyanamide/[N(CN)2] , dca), [Cd(N(CN)2)2(phen)]n (1) and [Cd(N(CN)2)2(2,2?-bipy)]n (2), have been synthesized and structurally characterized. The cadmium(II) centers in 1 are connected through single or double end-to-end dca bridging ligand to form a 2-D layer structure, which furthermore condense into a 3-D structure through the p /p interaction between aromatic rings of adjacent layers. In 2, the cadmium(II) coordination sphere is a distorted octahedron, bound to four dca ligands and one chelate 2,2?-bipy ligand, and the adjacent cadmium(II) centers are bridged by the double end-to-end m1,5-N /C /N /C/N to form an extended structure with a zigzag 1-D chain, and a 2-D layer structure results from the p /p interactions of the adjacent chains. Crown Copyright # 2002 Published by Elsevier Science Ltd. All rights reserved. Keywords: Cadmium complexes; Dca ligand; Double end-to-end; Zigzag chain; p /p interaction
1. Introduction Metal-organic frameworks are widely regarded as promising materials for application in catalysis, separation and molecular recognition [1]. There have been numerous reports in which N-donor bridging ligands are used to form infinite metal-organic polymeric frameworks [2]. Dicyanamide, [N(CN)2], was selected due to its coordination versatility ranging from being monodentate to m4- coordination, and thus provides a suitable ‘building block’ for assembling novel inorganic/organic hybrid materials. Monodentate (terminal) coordination occurs in [Cu(II)(o -phen)2{N(CN)2}][C(CN)3] [3,3a], [Cu(II)(o -phen)2{N(CN)2}2] (o-phen /o-phenanthroline) [3b] and [Zn3(OAc)4(4,4?-bipy)3{N(CN)2}2] [3c]. Bidentate coordination has often been observed and
* Corresponding author. Tel.: 86-591-379-2460; fax: 86-591371-4946. E-mail address: [email protected] (M.-C. Hong).
was reported for Me2Sn[N(CN)2]2 [3d], Me3Sn[N(CN)2] [3d], two polymorphs of Ag[N(CN)2] [3e,3f], and Mn[N(CN)2]2(pyz) (pyz /pyrazine) [3g,3h]. Tri-coordinate m3-[N(CN)2] is observed in the rutile-type class of molecule-based magnets, M(II)[N(CN)2]2 (M /Co or Ni) [3i]. Unusual m4 coordination [1e] is also known and was found in the structures of Me2Tl[N(CN)2] [3j]. Structures reported recently include M(dca)2L2 chains, (4,4) sheets, diamond-like works, interpenetrating networks, molecular tubes and self-penetrating works [4]. In these materials, s-bond formation occurs through lone pair donation of the nitrile N atoms to an octahedral metal center. Our goal was to prepare and characterize new low-dimensional solids consisting of divalent transition metal complexes with the dicyanamide ligand. Herein, we report the syntheses, crystal structures, and vibrational properties of [Cd(N(CN)2)2(phen)]n (1) and [Cd(N(CN)2)2(2,2?-bipy)]n (2), the first structurally characterized cadmium(II) dicyanamide complexes.
0277-5387/02/$ - see front matter Crown Copyright # 2002 Published by Elsevier Science Ltd. All rights reserved. PII: S 0 2 7 7 - 5 3 8 7 ( 0 2 ) 0 0 8 6 8 - 9
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2. Experimental
Table 1 Crystallographic data for the title two complexes
2.1. Materials and physical measures Elemental analyses were determined on an Elementar Vario ELIII analyzer. IR spectra were measured as KBr pellets on a Nicolet Magna 750 FT IR spectrometer in the range of 200/4000 cm 1. All reagents were commercially available and used as received. 2.2. Synthesis of the complexes 2.2.1. [Cd(N(CN)2)2(phen)]n (1) To an aqueous solution (20 ml) of Cd(NO3)2 ×/4H2O (0.155 g, 0.5 mmol), sodium dicyanamide (0.09 g, 1 mmol) was added. After stirring the mixture for about 30 min, the dmf solution (10 ml) of phen was added into it. The above mixture was stirred and heated for 1 h, then filtered when it was still hot. Well shaped crystals of [Cd(N(CN)2)2(phen)]n were obtained from the mother liquor by slow evaporation at room temperature (r.t.) for several days. They were filtered off, washed with a small mount of water, and dried in air. Yield 78%. Calc. for C16H8CdN8: C, 45.21; H, 1.88; N, 26.37. Found: C, 44.89; H, 2.01; N, 27.68%. 2.2.2. [Cd(N(CN)2)2(2,2?-bipy)]n (2) The compound was synthesized as 1 except 2,2?-bipy instead of phen. Yield 78%. Calc. for C14H8CdN8: C, 41.93; H, 2.00; N, 27.95. Found: C, 41.67; H, 1.85; N, 29.21%. 2.3. X-ray crystallography Single crystals with approximate dimensions 0.52 / 0.48 /0.40 mm for 1 and 0.42 /0.30 /0.25 mm for 2 were selected and coated with epoxy glue. Data collections was carried out on a Siemens Smart CCD diffractometer equipped with graphite-monochromated ˚ ) at 298 K. Intensities Mo Ka radiation (l/0.71073 A of both 1 and 2 were corrected for empirical absorption based on SADABS scan technique [5]. Their structures were solved by direct methods and all calculations were performed using the SHELXL-PC program [6]. The positions of H atoms were generated geometrically ˚ ), assigned isotropic thermal (C /H bond fixed at 0.96 A parameters. The structure was refined by full-matrix least-squares minimization of S(Fo/Fc)2 with anisotropic thermal parameters for all atoms except the H atoms. Table 1 gives a structure determination summary and Table 2 and Table 3 list the selected bond lengths and angles.
Empirical formula Formula weight Temperature (K) ˚) Wavelength (A Crystal system Space group Unit cell dimensions ˚) a (A ˚) b (A ˚) c (A a (8) b (8) g (8) ˚ 3) V (A Z Dcalc (Mg m 3) Absorption coefficient (mm 1) F (000) Crystal size (mm) u Range for data collection (8) Index ranges
Reflections collected Refinement method Data [I 2s (I )]/parameters Goodness-of-fit on F 2 R1 indices (I 2s (I )) Wr2 indices (all data) Largest difference peak ˚ 3) and hole (e A
1
2
C16H8CdN8 424.70 293(2) 0.71073 monoclinic P 2(1)/c 3D 10.1502(3) 10.9815(4) 14.5839(4) 90 99.609(1) 90 1602.78(9) 4 1.760 1.379
C14H8CdN8 400.34 293(2) 0.71073 monoclinic C 2/c 2D 6.6849(10) 17.476(2) 13.231(2) 90 91.142(3) 90 1545.4(4) 4 1.722 1.424
832 0.30 0.25 0.15 2.03 /25.06
784 0.27 0.21 0.15 2.33 /25.03
125 h 5 6, 135 k 5 12, 16 5 1 5 17 5804 Full-matrix leastsquares on F 2 2832/226
65 h 5 7, 20 5 k 5 10, 12 5 1 5 15 3086 Full-matrix leastsquares on F 2 1354/105
1.074 0.0328 0.779 0.513 and 0.471
1.005 0.0739 0.1818 0.44 and 0.734
Table 2 ˚ ) and angles (8) for [Cd(N(CN)2)2(phen)]n (1) Selected bond lengths (A Bond lengths Cd N(4) Cd N(3A) Cd N(7) C(1) N(1) C(2) N(3) C(3) N(4) C(4) N(6)
2.246(4) 2.291(4) 2.342(3) 1.143(5) 1.134(5) 1.123(5) 1.136(5)
Cd N(1) Cd N(8) Cd N(6B) C(1) N(2) C(2) N(2) C(3) N(5) C(4) N(5)
2.279(4) 2.322(3) 2.481(4) 1.291(5) 1.298(5) 1.291(6) 1.284(6)
Bond angles N(4) Cd N(1) N(1) Cd N(3A) N(1) Cd N(8) N(4) Cd N(7) N(3A) Cd N(7) N(4) Cd N(6B) N(3A) Cd N(6B) N(7) Cd N(6B)
94.30(16) 96.48(14) 98.04(13) 94.58(14) 98.51(12) 89.17(16) 177.70(13) 81.62(12)
N(4) Cd N(3A) N(4) Cd N(8) N(3A) Cd N(8) N(1) Cd N(7) N(8) Cd N(7) N(1) Cd N(6B) N(8) Cd N(6B)
93.10(15) 165.83(15) 92.40(12) 162.10(12) 71.68(11) 83.01(13) 85.46(13)
Symmetry transformations used to generate equivalent atoms: (A) x , y1/2, z1/2; (B) x1, y , z2; (C) x , y1/2, z1/2 for complex 1.
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Table 3 ˚ ) and angles (8) for [Cd(N(CN)2)2(2,2?-bipy)]n Selected bond lengths (A (2)
3. Results and discussion
Bond lengths Cd N(2A) Cd N(1) Cd N(4B) N(2) C(6) N(3) C(7)
2.304(12) 2.322(9) 2.346(13) 1.108(14) 1.252(16)
Cd N(2) Cd N(1A) Cd N(4C) C(6) N(3) C(7) N(4)
2.304(12) 2.322(9) 2.346(13) 1.237(16) 1.099(16)
3.1. IR spectroscopic study
Bond angles N(2A) Cd N(2) N(2) Cd N(1) N(2) Cd N(1A) N(2A) Cd N(4B) N(1) Cd N(4B) N(2A) Cd N(4C) N(1) Cd N(4C) N(4B) Cd N(4C)
103.7(5) 93.2(4) 162.6(4) 89.8(4) 95.5(4) 86.7(4) 89.2(4) 174.3(6)
N(2A) Cd N(1) N(2A) Cd N(1A) N(1) Cd N(1A) N(2) Cd N(4B) N(1A) Cd N(4B) N(2) Cd N(4C) N(1A) Cd N(4C)
162.6(4) 93.2(4) 70.4(5) 86.7(4) 89.2(4) 89.8(4) 95.5(4)
Symmetry transformations used to generate equivalent atoms: (A) x , y , z1/2; (B) x , y , z ; (C) x , y , z1/2.
At room temperature, the solid state infrared spectrum depicts several nCN bands at 2301m, 2260(sh), 2216s, 2177s, 2156s cm 1 in complex 1 and 2303m, 2206(sh), 2229s, 2156s cm 1 in complex 2, which are attributed to nsym/nasym(C /N), nasym(C /N) and nsym(C/N) modes, and are comparable to those of related compounds in Table 4. These bands differ significantly from those of Na[N(CN)2], which are at 2129, 2232 and 2286 cm1 [7]. The bands at 1365m, 916m in 1 and 1344m, 916m in 2 are assigned to nasym(C/N) and nsym(C /N), respectively.
Table 4 Comparison of nCN absorption of selected M(II)[N(CN)2]2Ln (n 1 or 2) complexes Complexes
n asym n sym (C N)
nasym(C N)
nasym(C N)
Reference
Mn[N(CN)2]2(py) Fe[N(CN)2]2(MeOH)2 Co[N(CN)2]2{iz}2 Ni[N(CN)2]2(tetramepz)2 Co[N(CN)2]2(2-meiz)2 Pd[N(CN)2]2{P(C6H5)3}2 Cu[N(CN)2]2(iz)2 [Cd(N(CN)2)2(phen)]n [Cd(N(CN)2)2(2,2?-bipy)]n
2295s 2306(sh), 2274m 2281s 2285vs 2279s 2310m 2292s 2301m,2260(sh) 2303m
2234m 2254s 2246s 2235(sh) 2250s 2240s 2250m 2216s 2229s
2167s 2178s,2154m 2185vs 2212vs,2165vs 2180vs,2150w 2180vs 2190s 2177s,2156s 2156s
[3g] [9] [10] [11] [10] [12] [13] this work this work
Fig. 1. An
ORTEP
drawing of [Cd(N(CN)2)2(phen)]n (1) with atomic numbering scheme.
J.-H. Luo et al. / Polyhedron 21 (2002) 893 /898
896
Fig. 2. The 2-D layer structure of [Cd(N(CN)2)2(phen)]n (1) (the terminal ligand Phen is omitted for clarity)
3.2. Crystal structure analysis 3.2.1. Crystal structure of complex 1 Fig. 1 shows an ORTEP [8] diagram of the coordination sphere of the Cd(II) ion and atom labeling in [Cd(N(CN)2)2(phen)]n (1). Each cadmium(II) atom lies on an inversion center, and is connected to three other cadmium(II) centers through four dca ligands, one double end-to-end dca bridge to one cadmium(II) atom and two single end-to-end dca bridges to another two cadmium(II) atoms. Thus, all cadmium atoms form
a 2-D layer structure through both the double end-toend dca bridges and single end-to-end dca bridges as in Fig. 2, and furthermore generate a 3-D structure through the weak p/p interaction between aromatic ˚ , as shown rings of adjacent layers with distances 3.584 A in Fig. 3. Each cadmium(II) center is six-coordinated and display a distorted octahedral coordination, with two terminal N atoms of two different dca ligands [Cd/ ˚ ] and two N atoms of N(1), 2.279(4); Cd /N(4), 2,246 A the phen ligand [Cd /N(7), 2.342 (3); Cd /N(8), 2.322(3) ˚ ] in the equatorial plane, while the other two N atoms A of two dca ligands [Cd /N(3A), 2.291(4); Cd /N(6B), ˚ ] occupy the axial positions. Two kinds of 2.481(4) A bond angles may be found in the equatorial plane: the lower of 71.688 corresponding to the N(phen)/Cd / N(phen) bond angle and three greater N(phen)/Cd / N(dca) bond angles [N(1) /Cd /N(8), 98.04(13)8; N(4) / Cd /N(7), 94.58(14)8] and N(dca)/Cd /N(dca) bond angles [N(4) /Cd /N(1), 94.30(16)8]. The four equatorial donor atoms and the central cadmium(II) atom determine a plane with maximum deviation for Cd of / 0.1628(5) A˚. Approximate C2v symmetry is observed for the dca ligand with C(2) /N(3), C(1) /N(1), C(4) / N(6) and C(3) /N(4) bond distances of 1.134(5), ˚ , respectively. The 1.143(5), 1.136(5) and 1.123(5) A lack of significant electron density near the amide nitrogen N2 and N5 results in longer C(1) /N(2), C(2) /N(2), C(3) /N(5) and C(4) /N(5) bond distances, ˚ , suggesting a small degree of p which average 1.291 A conjugation within the [N(CN)2] backbone [9].
Fig. 3. The 3-D structure of [Cd(N(CN)2)2(phen)]n (1) through the weak p /p interaction between adjacent layers
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Fig. 4. An ORTEP drawing of [Cd(N(CN)2)2(2,2?-bipy)]n (2) with atomic numbering scheme.
897
3.2.2. Crystal structure of complex 2 In complex 2, [Cd(N(CN)2)2](2,2?-bipy)], the adjacent cadmium(II) centers are bridged by the double end-toend m1,5-N /C /N/C /N to form an extended structure with a zigzag 1-D chain (Fig. 5). The cadmium(II) centers are bound to four dca ligands and one chelate 2,2?-bipy ligand (Fig. 4), the cadmium(II) coordination sphere is a distorted octahedron with two N atoms of ˚ ; Cd /N(2A), 2.304 A ˚ ] and two dca [Cd /N(2), 2.304 A two N atoms of the 2,2?-bipy ligand [Cd /N(1), 2.322(9) ˚ ; Cd /N(1A), 2.322(9) A ˚ ] in the equatorial plane, and A two N atoms of two other dca ligands [Cd /N(4B), ˚ ; Cd /N(4C), 2.346(13) A ˚ ] occupy the axial 2.346(13) A plane. The effect of the distortion is readily seen in cis N /Cd /N? bond angles, which vary from 70.4(5)8 to 103.(5)8 for N(1) /Cd /N(1A), N(1) /Cd /N(2) and N(2) /Cd /N(2A), respectively. [N(CN)2] bridging li-
Fig. 5. The chain structure of [Cd(N(CN)2)2(2,2?-bipy)]n (2).
Fig. 6. The 2-D structure of [Cd(N(CN)2)2(2,2?-bipy)]n (2) through the weak p /p interaction between adjacent chains.
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gands retain approximate C2v symmetry with C(7)/N(4) and C(6) /N(2) bond distances of 1.099(16) and ˚ , respectively. Weak p/p interactions are 1.108(14) A evident, with the shortest distance between the pyridine ˚ , thus forming a 2rings of adjacent chains being 3.641 A D sheets as in Fig. 6. [3]
4. Supplementary material Atomic coordinates, thermal parameters and bond lengths and angles for compounds 1 and 2 have been deposited at the Cambridge Crystallographic Center (CCDC). Any request to the CCDC for this material should quote the full literature citation and the reference numbers CCDC 162756 and 162757. Copies of this information may be obtained free of charge from The Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax: /44-1223-336033; e-mail: [email protected] or www:http://www.ccdc.cam.ac.uk).
Acknowledgements [4]
The authors are grateful to the National Nature Science Foundation of China and the Key Project of Chinese Academy of Science for financial support.
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